1. Field of the Invention
The present invention relates to an apparatus for manufacturing a single-crystal (such as semiconductor single crystal) by primarily using the Czochralski Method (CZ method)and method of manufacturing a single-crystal using the same.
2. Description of Prior Art
A single crystal lift device provided with a radiation screen or a radiation shield is well known. However, before commencing the lifting operation, a required amount of polycrystalline silicon lumps as a raw material must be supplied into the crucible of the single crystal lift device, and the radiation screen becomes an obstacle to the melting operation of the polycrystalline silicon. This is due to the fact that the radiation screen causes excessive melting time for the polycrystalline silicon, or alternatively adds the lower heater to expedite the melting of polycrystalline silicon. This will increase the cost of single crystal production. To solve the above-mentioned problem, proposals, such as in unexamined Japanese Patent Publication Hei 3-279290 and Hei 7-010683, have been offered. The former discloses suspending parts that can be screwed upward and downward and which are disposed on an upper board of the chambers whereby the radiation screen is suspended in the chamber. The latter discloses a radiation shield that can be driven to ascend and descend and which is suspended over a crucible by a wire of predetermined length, wherein the radiation shield is positioned by an automatic positioning system. Furthermore, as disclosed in unexamined Japanese Patent Publication Hei 6-92772, during melting of raw material for single crystal, instead of a seed chuck, a radiation shield suspension fixture is disposed in a seed holder. The lower end portion of the radiation shield is engaged with and is pulled up in advance by the radiation shield suspension fixture. After the polycrystalline silicon lumps have been melted and before commencing the lifting operation, the radiation shield is disengaged with the radiation shield suspension fixture and the pressure within the chamber is brought back to that of the outside air, then the radiation shield suspension fixture is detached from the seed holder on which the seed chuck with crystal seed mounted thereon is thereafter installed.
However, in conventional devices, both in Hei 3-279290 and 7-010683, an extra mechanism for driving the radiation screen or shield upward and downward is required, resulting in increased complexity and cost of the device. Furthermore, in Hei 6-92772, after the radiation screen has been hooked at a predetermined location, it has to be elevated to approach the pull chamber, then the radiation shield suspension fixture must be swapped for the seed chuck by the operator in a normal atmosphere. Therefore, it takes about 30 minutes to cool down the fixtures accommodated within the pull chamber and to turn the environment into a low pressure argon atmosphere. Thus, the above device suffers from such problems as low efficiency and difficulty in process automation.